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Boston Celtics star Jayson Tatum has agreed on a five-year, $314 million contract extension, including a player option and trade kicker, sources told ESPN's Adrian Wojnarowski on Monday.

Tatum, 26, led Boston to its 18th NBA title with a five-game victory over the Dallas Mavericks in the NBA Finals, averaging 22.2 points, 7.8 rebounds and 7.2 assists as the Celtics passed their forever rivals, the Los Angeles Lakers, for the most championships in league history.

The 6-foot-9 forward, who was drafted third overall by the Celtics in 2017, has developed into one of the NBA's top two-way talents on the wing, partnering with Jaylen Brown -- whom Boston signed to what was a record extension a year ago -- to form arguably the best wing tandem in the league today.

The Celtics also agreed to an extension with guard Derrick White earlier Monday. Boston now has every member of its starting lineup under contract through at least 2025-26.

Tatum is a five-time All-Star and four-time All-NBA selection, including being named to the All-NBA first team the past three seasons. After winning a gold medal at the Tokyo Olympics in 2021, he is also set to be part of Team USA's entry in the Paris Olympics this summer as the men's national team looks to claim its fifth consecutive gold medal.

ESPN's Tim Bontemps contributed to this report.